Archive: Dec 2015

  1. Intercontinental Attack UAVs

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    In the middle of the Second World War the Japanese launched a series of complex attacks using balloons on continental USA. One can argue whether these attacks can be considered as UAVs, but in my mind they fit a large part of the definition.  The hydrogen balloons, about 30ft in diameter carried a range of explosive and incendiary munitions.    The key to the weapon, from Japanese eyes was that:

    - it was a cheap method to attack the USA

    - it utilized the “jet stream” of high altitude west to east winds across the Pacific

    - it was a genuine inter-continental weapon

    - the weapon, like modern UAVs that pose a threat, avoided traditional defenses and arrived by a new “vector"

    - if successful, the Japanese recognized that the explosive or incendiary effects would be limited but the potential to have a strategic effect in terms of public perception within the population of the USA was significant. The Japanese judged that a small degree of success would have the same effect in the USA that the Doolittle raid had on Japan, in terms of demonstrating the vulnerability to long range attack, and the consequent effect on morale, and perception.

    Although the effect of the balloons was very limited, the number of UAVs launched was remarkable - over 9300 launched and at least 300 were found or observed in the USA in late 1944-1945.   It was thought by the Japanese that about 10% of the weapons would successfully cross the ocean, and indeed modern researchers think that figure is not far out - Most are likely to have ended up over unpopulated areas.  A total of six deaths were caused, all from a single balloon. Importantly the mix of lack of successful effects and wartime information control meant that the US public had little or no knowledge of the threat, defeating the public impact of the attack expected by the Japanese   So while the weapon can be considered a failure, the ingenious nature of the devices is worthy of consideration today as are aspects of the tactic, particularly the use of a large number of weapons used, to counter the small % expected to attack the targets.

    In some ways the balloons were “programmed”, not with software as modern UAVs are, but with simple timers and altimeters.  The balloons were programmed to counter the effects of the sun’s heat that would cause the balloon to rise and fall. The altimeter controlled a ballast system and a valve to release gas. ballast was dropped if the balloon fell below 30000 ft and hydrogen was vented above 38,000 ft. They were “programmed" to remain in the jet stream at 30,000 ft, and the expected speed of the jet stream then was used to set a timing device that would release the munitions when the balloons were expected to be over continental USA.  There was a plan for the balloons to deliver biological warfare weapons, possibly anthrax and cowpox, but this plan was never approved.


    Interestingly some of the early balloons carried radio transmitters t allow the balloons speed and height to be transmitted back, in order to allow more accurate “programming” of later balloons.   Once the balloons started to be discovered, no-one initially assessed that the launch point was all the way over in Japan, so a lot of effort was spent looking for evidence of closer launch points such as submarines or submarine infiltrated land parties. One theory also investigated was that the balloons were being launched from Japanese-American internment camps.  In an interesting technical intelligence program the US military carefully analyzed the sand in the sandbags from a recovered balloon to establish that the sand was evidently from the western shores of the Pacific and not mid-Pacific or West Coast USA.

    A very detailed report, issued in 1973, is available from the Smithsonian and well worth a read.

    The following factors about the Japanese balloon attacks are worthy of consideration when thinking about threats from UAVs today:

    -  Drones provide a cheap way of introducing a threat

    -  Numbers of drones can out-do an individual small chance of success - setting a swarm might result in a small number "get through”

    -  Theoretically the threat can be varied - and could include explosive incendiary or biological weapons.

    -  Modern drones with much more control can introduce a threat to within feet or inches of a targets, and traditional perimeter based security is negated or circumvented.

    -  Discovering where UAVs are launched from is a key requirement in a response capability

    -  Three dimensional attacks are always challenging to detect

    - The public perception of the threat may cause a greater effect than the weapon system itself presents

    All these factors are woven into the modern and innovative drone defense systems being developed by D13. Although the technology in these historical Japanese drones is primitive we recognize that the lessons of history always provide useful insights.

    In my next post I’ll discuss the 100,000 UAVs released by the British to drift over WW2 Germany designed to disrupt the power infrastructure.